Spark plug



Mar. 6', 1923.

C. W. BREWSTER SPARK PLUG y ..l rlllnllln lrlilllllllllvllllll lull Filed July 5, 1918 TT, FH..

CHARLS W. BBEWSTER, OF,NEW YORK, N. 'Y., `ASSllfl-)IJOIB' TO THE BRWSTER-GOLD- SMITH CORPORATION, INC., 0F NEW' YORK, Y., A CORPORATION OF N'EW YORK;

SPARK rime.v

y Application led J'uly 5, 1918. Serial No. 243,395. A

To allfwhom it may concern:

Be it known that I, CHARLES W. B Bnws- TER, a citizen of the United States, and a resident of the borough of Manhattan, in the city, county, and State of New York, have invented certain new and useful lmprovements in Spa-rk Plugs, of which the following is a specification.

rThe object of the invention is to provide an improved spark plug for internal combustion engines, and particularly for aeroplane engines, wherein the temperature and lubricating conditions are detrimental to ordinary plugs. To this end the invention may be said to comprise the parts, improvements and combinations hereinafter described and more particularly pointed out in the claims.

ln the accompanying drawings:

Fig. l is an elevation of the spark plug with the valve and valve-retainer removed;

Fig. 2 is an axial section showing the valve l seated in the position which it occupies during the compression stroke of the cylinder, and indicating a means for delivering ai jet of liquid fuel into the intake;

Fig.,3 is a cross-section on the line 3 3 of Fig. 2; f

Fig. 4 is a view looking at the inner end of the plug; and

Fig. 5 is an elevation of thefcentra'l elecy trode unit. i

The spark plug has a shell l,l which is screwed into an opening in the engine, as usual. The shell is provided in the upper' part of its interior with a downward-facing beveled shoulder 2. An insulator 3 is inserted upward into the shell and is provided with ya beveled centralizing shoulder 4 to co-operate with the shoulder 2. A central conductor rod 5 having a kshoulder 6 at its lower end to bear upon the end of the in'- sulator 3 passes through this insulator and projects above its top. An outer hollow insulator 7 encloses the projecting portion of the insulator 3 and rests upon the top of the shell.` The parts are clamped together by a nut 8 screwed upon the upper end of the rod. rlhis nut may be formed,` with a ball to receive an electricalconnection of the glovefastenerftypeor any other suitable connec tion maybe provided. The rod 5 preferably 'passes loosely through the insulator 3, and

tight joints are insured by cement gaskets between the shoulders 2 and 4 and between the shoulder and the end of 'the insulator.

The insulator 3 is desirably of porcelain,

with an inner sleeve 9 of rolled mica to pre- -vent leakage of current in event of .cracking base of which forms the shoulder 6, to which reference has been made. rllhis cup is preferably of substantially the saine external diameter as Vthe 'lower part of the insulator l3, and between these parts and the shell is an annular space 11.` An outturned ange 12 on the edge of the cup 10 oonstitutesan electrode terminal, from which the spark passes to the shell at any point around the circumference. lt will thus be seen that l provide an annular electrode presenting a hollow interior to the firing chamber and connected with the central conductor `by a cup which yrecedes upward into the interior of the shell.

rlhe annular electrode is located inside the mouth of the shell as shown. .ln this way the central member presents the least amount of metal to the heat of the ri'ng chamber and Vthe terminalv structure is protected `within the shell. The cup l() is preferably, though not necessarily, cylindrical, and its wall is made thin. The cup is advantageously made separately from the rod, but united integrally therewith by welding. The cup constitutes a barrier to prevent lubricating oil being thrown into the annular space between the central parts and the shell. In this connection. it willbe noted that the gap between theannular electrode and the edge of the shell'is too narrow to aEord vready ingress for oil, and the slight amount which may enter is swept out by the means about t0 be described.

The construction described above,while advantageous where the temperatures are not too high and superior to ordinary designs,

would not be suiicient in itself to prevent .the electrode burning off under the extreme ce l by a slotted opening 14, which is formed by a circular grooveil in the interior of the shell, which groove constitutes a distributing chamber at thev upper end of the annular passage l1 and cuts through the side wall 16 at the region of the intake. A bushing 17 is screwed into the intake, outside of the wall 16, and coniines a check-valve 18. The said check-valve has a tubular skirt 19, which is guided in the passage of the bushing, and an enlarged head 20 which operates in the valve chamber 21, the'laterally pro,- jecting rim of this head being formed with an annular beveled seat 22 which co-operates with a corresponding seat 23 'formed at the inner end of the guide passage in the bushing. @penings 24 are cut through the skirt 19 adj arent the head of the valve.

In operation, on each suction Stroke of the engine pistons the valve 18 is drawn inward, thus exposing the openings 24 to the chamber 21 and permitting air to rush into this chamber and through the opening 14, which is not entirely covered by the head of the valve, into the interior of the plug, whence it passes downward through the annular passage 11 and around the ring electrode 12 into the firing chamber, thus cooling the highly heated parts. For purposes of removing any deposits of grease and carbon in the plug, a small supply of gasoline is introduced with Vthe air, but instead of the gasoline and air entering the plug wholly as a vaporized mixture, means are provided Vfor delivering the gasoline to the intake in liquid form, so that it is swept in at least partially in the condition which is most effective for cutting greasy and carbonaceous deposits. In the illustrative form, a small pipe 25 connected with an elevated gasoline reservoir 26 extends inproxlmlty to the open intake and is provided opposite it with a fine jet orifice 27. The very small stream of gasoline from this orifice plays continuously into the intake, and, upon each suction stroke of the piston of the corresponding engine cylinder,

effectively Lamers the valve 18 opens and the small accumulation of gasoline is sprayed into the plug by the inrush of air. Needless to say, other specifically different forms of means for automatically delivering liquid fuel to the intake of the sparkv plug may be employed, and l have found that under certain conditions the liquid fuel supply may be dispensed with and air alone used to cool and clean the plug.

@ne of the advantages of the invention is that the plug is so eiiectively safeguarded against ouling that ordinary lubricating oil may be used for the engine cylinders in place of castor oil, the supply of which is limited. y

ltwill be understood that in the foregoing speciication upper means in the direction toward the part of the plug which is'outside the engine, while lower means in the direction toward the part of the plug which is inside the engne. Of course, the plug may be mounted in any positionvertically, horizontally, or at an inclination.

wWhat l claim as new is:

rlhe combination of a spark plug having an interior cooling and cleaning passage and a suction intake thereto in the upper part of the plug, said intake'having a valve chamber and a guide passage leadingto said chamber, aI check-valve having a tubular skirtguided in said guide passage and provided with lateral openings, and an enlarged head operative in said chamber and having its projecting rim formed to seat at the end of the guide passage.

ln testimony whereof, l have signed my name to this specification, in the presence of two subscribing witnesses.

CHARLES W. BREWSTER. Witnesses.: W. F. BIssING,

J. RENITZ. 

